Refrigerator lubricating oil and mixed composition for refrigerator

ABSTRACT

Disclosed herein is a mixed composition for a refrigerator, the mixed composition containing: a refrigerant containing at least one unsaturated fluorinated hydrocarbon compound selected from compounds represented by the following molecular formula (1): C p F r H s  (1), provided that the compound has one or more carbon-carbon unsaturated bond in a molecule: and a refrigerator lubricating oil containing, as a major component, a polyoxyalkylene glycol compound represented by the following general formula (2), and containing a phenothiazine compound in an amount of 1.0% by mass or more based on the total amount of the refrigerator lubricating oil: R 1 —[(OR 2 ) m —OR 3 ] n  (2). A mixed composition for a refrigerator is provided having a lower possibility of autoignition in a high temperature environment even during unexpected leakage in a refrigerator using a refrigerant containing a slightly flammable refrigerant. A refrigerator lubricating oil is provided that is capable of being applied to the mixed composition.

TECHNICAL FIELD

The present invention relates to a mixed composition for a refrigeratorusing a refrigerant containing an unsaturated fluorinated hydrocarboncompound, and a refrigerator lubricating oil used with a refrigerantcontaining an unsaturated fluorinated hydrocarbon compound.

BACKGROUND ART

As the refrigerant for a refrigerator, a chlorine-containing compound,such as a chlorofluorocarbon, has been widely used, but in considerationof the environment protection, it is being replaced by a compoundcontaining no chlorine, such as a hydrofluorocarbon (HFC), and a naturalrefrigerant, such as carbon dioxide.

Examples of the hydrofluorocarbon in practical use include a saturatedhydrofluorocarbon (which may be hereinafter referred to as a saturatedHFC), which is represented by 1,1,1,2-tetrafluoroethane,difluoromethane, pentafluoroethane, and 1,1,1-trifluoroethane (which maybe hereinafter referred to as R134a, R^(32,) R125, and R143a,respectively).

For a car air-conditioner, however, it is currently difficult to usecarbon dioxide requiring high pressure as the major component of arefrigerant, and the use of a saturated HFC having a high global warmingpotential is also being avoided.

Under the circumstances, it is being considered in recent years to usean unsaturated fluorinated hydrocarbon compound, such as HFO1234ze andHFO1234yf, as a refrigerant capable of being used in the current carair-conditioner, irrespective of the low global warming potentialthereof. Examples of a base oil of a refrigerator lubricating oilcapable of being combined with the refrigerant containing theunsaturated fluorinated hydrocarbon compound include anoxygen-containing compound, such as a polyoxyalkylene glycol compound, apolyol ester compound, and a polycarbonate compound (see PTLs 1 to 3).

An open type car air-conditioner as an example of the refrigerator usesa rubber hose for the piping thereof, and thus water tends to enter thesystem. Therefore, a polyoxyalkylene glycol compound is used rather thana polyol ester compound, which tends to undergo hydrolysis throughcontact with water, so as to form a carboxylic acid causingdeterioration.

In the case of a car air-conditioner, the mixture of the refrigeratorlubricating oil and the refrigerant (which is referred to as a mixedcomposition for a refrigerator) in the refrigerator is necessarilyassumed to leak into the engine compartment due to the breakage of therefrigerator in an unanticipated situation, for example, a car accident.

The refrigerant, the use of which is being considered in recent years,such as HFO1234ze and HFO1234yf, has slight flammability and is usedwith the refrigerator lubricating oil containing the flammablepolyoxyalkylene glycol compound, and therefore there is a possibilitythat the leaking mixed composition for a refrigerator ignites under thehigh temperature environment in the engine compartment in anunanticipated situation.

Accordingly, for a car air-conditioner, such a refrigerator lubricatingoil is demanded that is capable of preventing autoignition under thehigh temperature environment in the engine compartment, i.e., has a highautoignition point.

CITATION LIST Patent Literatures

PTL 1: JP 2008-115266 A

PTL 2: JP 2011-046881 A

PTL 3: JP 2011-046884 A

SUMMARY OF INVENTION Technical Problem

An object of the present invention is to provide a mixed composition fora refrigerator that has a less possibility of autoignition under a hightemperature environment even in an unexpected leakage thereof in arefrigerator using a refrigerant containing a slightly flammablerefrigerant, and to provide a refrigerator lubricating oil that iscapable of being applied to the mixed composition for a refrigerator.

Solution to Problem

As a result of earnest investigations accumulated by the presentinventors, it has been found that the autoignition point of therefrigerator lubricating oil can be increased by combining arefrigerator lubricating oil containing a polyoxyalkylene glycolcompound having a particular structure as a major component andcontaining a phenothiazine compound, with a refrigerant containing anunsaturated fluorinated hydrocarbon compound, and thus the presentinvention has been completed based on the knowledge.

Accordingly, the present invention provides the following.

]1] A mixed composition for a refrigerator, containing:

a refrigerant containing at least one unsaturated fluorinatedhydrocarbon compound selected from compounds represented by thefollowing molecular formula (1):

C_(p)F_(r)H_(s)   (1)

wherein p represents an integer of from 2 to 6; r represents an integerof from 1 to 11; and s represents an integer of from 1 to 11, providedthat the compound has one or more carbon-carbon unsaturated bond in amolecule, and

a refrigerator lubricating oil containing, as a major component, apolyoxyalkylene glycol compound represented by the following generalformula (2), and containing a phenothiazine compound in an amount of1.0% by mass or more based on the total amount of the refrigeratorlubricating oil:

R¹—[(OR²)_(m)—OR³]_(n)   (2)

wherein R¹ is selected from a hydrogen atom, an alkyl group having anumber of carbon atoms of from 1 to 10, an acyl group having a number ofcarbon atoms of from 2 to 10, an aliphatic hydrocarbon group having anumber of carbon atoms of from 1 to 10 and having from 2 to 6 bondingsites, and a substituent having a number of carbon atoms of from 3 to 15and containing a heterocyclic ring which has oxygen and/or sulfur as aheteroatom; R² represents an alkylene group having a number of carbonatoms of from 2 to 4; R³ represents a hydrogen atom, an alkyl grouphaving a number of carbon atoms of from 1 to 10, or an acyl group havinga number of carbon atoms of from 2 to 10; n represents an integer offrom 1 to 6; and m represents a number such that an average value of m×nis from 6 to 80.

[2] The mixed composition for a refrigerator according to the items [1],wherein the refrigerant consists only of the unsaturated fluorinatedhydrocarbon compound.

[3] The mixed composition for a refrigerator according to the items [1]or [2], wherein the unsaturated fluorinated hydrocarbon compound is afluoride of propene.

[4] The mixed composition for a refrigerator according to the items [3],wherein the fluoride of propene is at least one selected from isomers ofpentafluoropropene, 3,3,3-trifluoropropene, and1,3,3,3-tetrafluoropropene.

[5] The mixed composition for a refrigerator according to any one of theitems [1] to [4], wherein the phenothiazine compound is at least oneselected from methoxyphenothiazine, 2-(trifluoromethyl)phenothiazine,2-acetylphenothiazine, 1-azaphenothiazine, and a phenothiazine-styrenederivative.

[6] The mixed composition for a refrigerator according to any one of theitems [1] and [3] to [5], wherein the refrigerant contains at least onesaturated fluorinated hydrocarbon compound selected from1,1-difluoroethane, trifluoroethane, tetrafluoroethane, andpentafluoroethane.

[7] The mixed composition for a refrigerator according to any one of theitems [1] to [6], wherein the mixed composition for a refrigerator isused for a hot water supply system or a refrigerating and heating systemof a car air-conditioner, an electric car air-conditioner, a gas heatpump system, an air conditioner, a refrigerating chamber, an automaticvending machine, or a showcase.

[8] The mixed composition for a refrigerator according to any one of theitems [1] to [6], wherein the mixed composition for a refrigerator isused for a car air-conditioner or an electric car air-conditioner.

[9] The mixed composition for a refrigerator according to any one of theitems [1] to [7], wherein the mixed composition for a refrigerator isused for a hot water supply system or a refrigerating and heatingsystem, and the system has a water content therein of 300 ppm by mass orless and a residual air partial pressure therein of 10 kPa or less.

[10] A refrigerator lubricating oil that is used for a refrigerantcontaining at least one unsaturated fluorinated hydrocarbon compoundselected from compounds represented by the following molecular formula(1):

C_(p)F_(r)H_(s)   (1)

wherein p represents an integer of from 2 to 6; r represents an integerof from 1 to 11; and s represents an integer of from 1 to 11, providedthat the compound has one or more carbon-carbon unsaturated bond in amolecule,

the refrigerator lubricating oil containing, as a major component, apolyoxyalkylene glycol compound represented by the following generalformula (2), and containing a phenothiazine compound in an amount of1.0% by mass or more based on the total amount of the refrigeratorlubricating oil:

R¹—[(OR²)_(m)—OR³]_(n)   (2)

wherein R¹ is selected from a hydrogen atom, an alkyl group having anumber of carbon atoms of from 1 to 10, an acyl group having a number ofcarbon atoms of from 2 to 10, an aliphatic hydrocarbon group having anumber of carbon atoms of from 1 to 10 and having from 2 to 6 bondingsites, and a substituent having a number of carbon atoms of from 3 to 15and containing a heterocyclic ring which has oxygen and/or sulfur as aheteroatom; R² represents an alkylene group having a number of carbonatoms of from 2 to 4; R³ represents a hydrogen atom, an alkyl grouphaving a number of carbon atoms of from 1 to 10, or an acyl group havinga number of carbon atoms of from 2 to 10; n represents an integer offrom 1 to 6; and in represents a number such that an average value ofm×n is from 6 to 80.

[11] A lubricating method including using a refrigerator lubricating oilin a refrigerator using a refrigerant containing at least oneunsaturated fluorinated hydrocarbon compound selected from compoundsrepresented by the following molecular formula (1):

C_(p)F_(r)H_(s)   (1)

wherein p represents an integer of from 2 to 6; r represents an integerof from 1 to 11; and s represents an integer of from 1 to 11, providedthat the compound has one or more carbon-carbon unsaturated bond in amolecule,

the refrigerator lubricating oil containing, as a major component, apolyoxyalkylene glycol compound represented by the following generalformula (2), and containing a phenothiazine compound in an amount of1.0% by mass or more based on the total amount of the refrigeratorlubricating oil:

R¹—[(OR₂)_(m)—OR³]_(n)   (2)

wherein R¹ is selected from a hydrogen atom, an alkyl group having anumber of carbon atoms of from 1 to 10, an acyl group having a number ofcarbon atoms of from 2 to 10, an aliphatic hydrocarbon group having anumber of carbon atoms of from 1 to 10 and having from 2 to 6 bondingsites, and a substituent having a number of carbon atoms of from 3 to 15and containing a heterocyclic ring which has oxygen and/or sulfur as aheteroatom; R² represents an alkylene group having a number of carbonatoms of from 2 to 4; R³ represents a hydrogen atom, an alkyl grouphaving a number of carbon atoms of from 1 to 10, or an acyl group havinga number of carbon atoms of from 2 to 10; n represents an integer offrom 1 to 6; and m represents a number such that an average value of m×nis from 6 to 80.

[12] A refrigerator including used therein:

a refrigerant containing at least one unsaturated fluorinatedhydrocarbon compound selected from compounds represented by thefollowing molecular formula (1):

C_(p)F_(r)H_(s)   (1)

wherein p represents an integer of from 2 to 6; r represents an integerof from 1 to 11; and s represents an integer of from 1 to 11, providedthat the compound has one or more carbon-carbon unsaturated bond in amolecule, and

a refrigerator lubricating oil containing, as a major component, apolyoxyalkylene glycol compound represented by the following generalformula (2), and containing a phenothiazine compound in an amount of1.0% by mass or more based on the total amount of the refrigeratorlubricating oil:

R¹—[(OR₂)_(m)—OR₃]_(n)   (2)

wherein R¹ is selected from a hydrogen atom, an alkyl group having anumber of carbon atoms of from 1 to 10, an acyl group having a number ofcarbon atoms of from 2 to 10, an aliphatic hydrocarbon group having anumber of carbon atoms of from 1 to 10 and having from 2 to 6 bondingsites, and a substituent having a number of carbon atoms of from 3 to 15and containing a heterocyclic ring which has oxygen and/or sulfur as aheteroatom; R² represents an alkylene group having a number of carbonatoms of from 2 to 4; R³ represents a hydrogen atom, an alkyl grouphaving a number of carbon atoms of from 1 to 10, or an acyl group havinga number of carbon atoms of from 2 to 10; n represents an integer offrom 1 to 6; and m represents a number such that an average value of m×nis from 6 to 80.

Advantageous Effects of Invention

According to the present invention, an object thereof is to provide amixed composition for a refrigerator that has a less possibility ofautoignition under a high temperature environment even in an unexpectedleakage thereof in a refrigerator using a refrigerant containing aslightly flammable refrigerant, and to provide a refrigeratorlubricating oil that is capable of being applied to the mixedcomposition for a refrigerator.

Description of Embodiments

Preferred embodiments of the present invention will be described indetail below.

[Mixed Composition for Refrigerator]

The mixed composition for a refrigerator of an embodiment of the presentinvention contains:

a refrigerant containing at least one unsaturated fluorinatedhydrocarbon compound selected from compounds represented by thefollowing molecular formula (1):

C_(p)F_(r)H_(s)   (1)

wherein p represents an integer of from 2 to 6; r represents an integerof from 1 to 11; and s represents an integer of from 1 to 11, providedthat the compound has one or more carbon-carbon unsaturated bond in amolecule, and

a refrigerator lubricating oil containing, as a major component, apolyoxyalkylene glycol compound represented by the following generalformula (2), and containing a phenothiazine compound in an amount of1.0% by mass or more based on the total amount of the refrigeratorlubricating oil:

R¹—[(OR²)_(m)—OR³]_(n)   (2)

wherein R¹ is selected from a hydrogen atom, an alkyl group having anumber of carbon atoms of from 1 to 10, an acyl group having a number ofcarbon atoms of from 2 to 10, an aliphatic hydrocarbon group having anumber of carbon atoms of from 1 to 10 and having from 2 to 6 bondingsites, and a substituent having a number of carbon atoms of from 3 to 15and containing a heterocyclic ring which has oxygen and/or sulfur as aheteroatom; R² represents an alkylene group having a number of carbonatoms of from 2 to 4; R³ represents a hydrogen atom, an alkyl grouphaving a number of carbon atoms of from 1 to 10, or an acyl group havinga number of carbon atoms of from 2 to 10; n represents an integer offrom 1 to 6; and m represents a number such that an average value of m×nis from 6 to 80.

The mixed composition for a refrigerator according to the presentinvention contains a refrigerator lubricating oil and a refrigerant. Therefrigerant and the refrigerator lubricating oil will be described inmore detail below.

[Refrigerant] <Unsaturated Fluorinated Hydrocarbon Compound>

The refrigerator lubricating oil according to the present invention isused for the following refrigerant. The refrigerant contains at leastone unsaturated fluorinated hydrocarbon compound selected from compoundsrepresented by the following molecular formula (1):

C_(p)F_(r)H_(s)   (1)

wherein p represents an integer of from 2 to 6; r represents an integerof from 1 to 11; and s represents an integer of from 1 to 11, providedthat the compound has one or more carbon-carbon unsaturated bond in amolecule.

The molecular formula (1) shows the kinds and the numbers of theelements in the molecule, and the formula (1) represents an unsaturatedfluorinated hydrocarbon compound having a number p of carbon atoms C offrom 2 to 6. With having a number of carbon atoms of from 2 to 6, theunsaturated fluorinated hydrocarbon compound can have physical andchemical properties, such as a boiling point, a freezing point, and anevaporation latent heat, that are required for a refrigerant.

In the molecular formula (1), the bond types of the p carbon atomsrepresented by C_(p) include a carbon-carbon single bond and anunsaturated bond, such as a carbon-carbon double bond. The carbon-carbonunsaturated bond is preferably a carbon-carbon double bond from thestandpoint of the stability, and the unsaturated fluorinated hydrocarboncompound preferably has 1 or more unsaturated bond, such as acarbon-carbon double bond, in the molecule thereof, with the numberthereof being preferably 1. Namely, at least one of the bond types ofthe p carbon atoms represented by C_(p) is more preferably acarbon-carbon double bond.

Preferred examples of the unsaturated fluorinated hydrocarbon compoundinclude fluorinated compounds of a linear or branched olefin having anumber of carbon atoms of from 2 to 6 and a cyclic olefin having anumber of carbon atoms of from 4 to 6.

Specific examples thereof include a fluorinated compound of ethylenehaving from 1 to 3 fluorine atoms introduced therein, a fluorinatedcompound of propene having from 1 to 5 fluorine atoms introducedtherein, a fluorinated compound of butene having from 1 to 7 fluorineatoms introduced therein, a fluorinated compound of pentene having from1 to 9 fluorine atoms introduced therein, a fluorinated compound ofhexene having from 1 to 11 fluorine atoms introduced therein, afluorinated compound of cyclobutene having from 1 to 5 fluorine atomsintroduced therein, a fluorinated compound of cyclopentene having from 1to 7 fluorine atoms introduced therein, and a fluorinated compound ofcyclohexene having from 1 to 9 fluorine atoms introduced therein.

Among these unsaturated fluorinated hydrocarbon compounds, a fluorinatedcompound of propene is preferred, a propene compound having from 3 to 5fluorine atoms introduced therein is more preferred, and preferredspecific examples thereof include isomers of pentafluoropropene,3,3,3-trifluoropropene, 1,3,3,3-tetrafluoropropene represented byHFO1234ze, and 2,3,3,3-tetrafluoropropene represented by HFO1234yf.

Among these, a propene compound having 4 fluorine atoms introducedtherein is more preferred, and 2,3,3,3-tetrafluoropropene represented byHFO1234yf is particularly preferred.

In the present invention, the unsaturated fluorinated hydrocarboncompound may be used solely or as a combination of two or more kindsthereof.

<Additional Component>

In the present invention, the refrigerant may be a mixed refrigerantthat contains an additional component in addition to the unsaturatedfluorinated hydrocarbon compound as necessary, and for example, maycontain a saturated fluorinated hydrocarbon compound.

The saturated fluorinated hydrocarbon compound is preferably afluorinated compound of an alkane having a number of carbon atoms offrom 2 to 4, and is preferably at least one selected from1,1-difluoroethane (R152a), a trifluoroethane, a tetrafluoroethane, anda pentafluoroethane, which are fluorides of ethane.

Examples of the trifluoroethane include 1,1,1-trifluoroethane (R143a)and 1,1,2-trifluoroethane (R143).

Examples of the tetrafluoroethane include 1,1,1,2-tetrafluoroethane(R134a) and 1,1,2,2-tetrafluoroethane (R134).

Examples of the pentafluoroethane include 1,1,1,2,2-pentafluoroethane(R125).

The saturated fluorinated hydrocarbon compound may be used solely or asa combination of two or more kinds thereof.

The refrigerant may contain carbon dioxide, and in this case, therefrigerant preferably contains the unsaturated fluorinated hydrocarboncompound, carbon dioxide, and an additional third component.Specifically, the refrigerant preferably contains1,3,3,3-tetrafluoropropene (HFO1234ze), carbon dioxide (R-744), and thethird component selected from difluoromethane (R32), 1,1-difluoroethane(R152a), fluoroethane (R161), 1,1,1,2-tetrafluoroethane (R134a),propylene, propane, and mixtures thereof.

The refrigerant preferably contains the unsaturated fluorinatedhydrocarbon compound represented by the molecular formula (1) as a majorcomponent. The term “containing as a major component” means that therefrigerant contains the compound in an amount of 50% by mass or morebased on the total amount of the refrigerant, and the content thereof ispreferably 70% by mass or more, more preferably 80% by mass or more, andfurther preferably 90% by mass or more, based on the total amount of therefrigerant. The additional component, such as the saturated fluorinatedhydrocarbon compound, is preferably not blended, and the refrigerantpreferably consists only of the unsaturated fluorinated hydrocarboncompound.

[Refrigerator Lubricating Oil] <Base Oil> (Polyoxyalkylene GlycolCompound)

The refrigerator lubricating oil according to the present inventioncontains, as a major component, a polyoxyalkylene glycol compoundrepresented by the following general formula (2):

R¹—[(OR²)_(m)—OR³]_(n)   (2)

wherein R¹ is selected from a hydrogen atom, an alkyl group having anumber of carbon atoms of from 1 to 10, an acyl group having a number ofcarbon atoms of from 2 to 10, an aliphatic hydrocarbon group having anumber of carbon atoms of from 1 to 10 and having from 2 to 6 bondingsites, and a substituent having a number of carbon atoms of from 3 to 15and containing a heterocyclic ring which has oxygen and/or sulfur as aheteroatom; R² represents an alkylene group having a number of carbonatoms of from 2 to 4; R³ represents a hydrogen atom, an alkyl grouphaving a number of carbon atoms of from 1 to 10, or an acyl group havinga number of carbon atoms of from 2 to 10; n represents an integer offrom 1 to 6; and m represents a number such that an average value of m×nis from 6 to 80.

In the general formula (2), the alkyl group in R¹ and R³ may be any ofstraight-chain, branched, and cyclic. Specific examples of the alkylgroup include a methyl group, an ethyl group, a n-propyl group, anisopropyl group, butyl groups of every kind, pentyl groups of everykind, hexyl groups of every kind, heptyl groups of every kind, octylgroups of every kind, nonyl groups of every kind, decyl groups of everykind, a cyclopentyl group, and a cyclohexyl group. When the number ofcarbon atoms of the alkyl group exceeds 10, there may be a case wherethe compatibility with the refrigerant is lowered to cause phaseseparation. The number of carbon atoms of the alkyl group is preferablyfrom 1 to 6.

The alkyl group moiety of the acyl group in R¹ and R³ may be any ofstraight-chain, branched, and cyclic. Specific examples of the alkylgroup moiety in the acyl group include the similar groups having anumber of carbon atoms of from 1 to 9 shown as the specific examples ofthe alkyl group. When the number of carbon atoms of the acyl groupexceeds 10, there may be a case where the compatibility with therefrigerant is lowered to cause phase separation. The number of carbonatoms of the acyl group is preferably from 2 to 6.

In the case where both R¹ and R³ each are an alkyl group or an acylgroup, R¹ and R³ may be the same as or different from each other.

In the case where n is 2 or more, the plural groups represented by R³ inone molecule may be the same as or different from each other.

In the case where R¹ is an aliphatic hydrocarbon group having a numberof carbon atoms of from 1 to 10 and having from 2 to 6 bonding sites,the aliphatic hydrocarbon group may be either chainlike or cyclic.Examples of the aliphatic hydrocarbon group having 2 bonding sitesinclude an ethylene group, a propylene group, a butylene group, apentylene group, a hexylene group, a heptylene group, an octylene group,a nonylene group, a decylene group, a cyclopentylene group, and acyclohexylene group. Examples of the aliphatic hydrocarbon group havingfrom 3 to 6 bonding sites include a residual group obtained by removinghydroxyl groups from a polyhydric alcohol, such as trimethylolpropane,glycerin, pentaerythritol, sorbitol, 1,2,3-trihydroxycyclohexane, and1,3,5-trihydroxycyclohexane.

When the number of carbon atoms of the aliphatic hydrocarbon groupexceeds 10, there may be a case where the compatibility with therefrigerant is lowered to cause phase separation. The number of carbonatoms thereof is preferably from 2 to 6.

In the case where R¹ is a substituent having a number of carbon atoms offrom 3 to 15 and containing a heterocyclic ring which has oxygen and/orsulfur as a heteroatom, substituents having tetrahydrofuran,methyltetrahydrofuran, tetrahydrothiophene, methyltetrahydrothiophene,furfuryl, or tetrahydrofurfuryl in the structure thereof, andderivatives derived from the substituents are preferred. Among these, R¹is preferably a tetrahydrofurfuryl group.

R² in the general formula (2) is an alkylene group having a number ofcarbon atoms of from 2 to 4, and examples of the oxyalkylene group as arepeating unit include an oxyethylene group, an oxypropylene group, andan oxybutylene group. The oxyalkylene groups in one molecule may be thesame as each other, and two or more kinds of oxyalkylene groups may alsobe contained. It is preferred that at least an oxypropylene unit iscontained in one molecule, and it is more preferred that 50% by mol ormore of an oxypropylene unit is contained in the oxyalkylene unit.

In the general formula (2), n represents an integer of from 1 to 6,which is determined by the number of bonding sites of R¹. For example,in the case where R¹ is an alkyl group or an acyl group, n is 1, and inthe case where R¹ is an aliphatic hydrocarbon group having 2, 3, 4, 5,or 6 bonding sites, n is 2, 3, 4, 5, or 6, respectively. m represents anumber such that an average value of m×n is from 6 to 80, and when theaverage value of m×n is outside the range, the object of the presentinvention cannot be sufficiently achieved.

The polyoxyalkylene glycol compound represented by the general formula(2) encompasses a polyoxyalkylene glycol having a hydroxyl group at theend thereof, and may be preferably used when the content of the hydroxylgroup is 50% by mol or less based on the total amount of the end group.When the content of the hydroxyl group exceeds 50% by mol, thehygroscopicity may be increased to lower the viscosity index, which isnot preferred.

The polyoxyalkylene glycol compound is preferably a polyoxypropyleneglycol dimethyl ether represented by the following general formula (3),a polyoxyethylene polyoxypropylene glycol dimethyl ether represented bythe following general formula (4), a polyoxypropylene glycol monobutylether represented by the following general formula (5), apolyoxypropylene glycol diacetate, or the like, from the standpoint ofthe economic efficiency and the effects.

wherein x represents a number of from 6 to 80.

wherein a and b each represents a number of 1 or more such that a totalthereof is from 6 to 80.

wherein x represents a number of from 6 to 80.

As for the polyoxyalkylene glycol compound represented by the generalformula (2), any one of those described in detail in JP 2-305893 A maybe used. In an embodiment according to the present invention, the term“containing the polyoxyalkylene glycol compound represented by thegeneral formula (2) as a major component” means that the refrigeratorlubricating oil contains the compound in an amount of 50% by mass ormore based on the total amount of the refrigerator lubricating oil, andthe content thereof is preferably 70% by mass or more, more preferably80% by mass or more, and further preferably 90% by mass or more, basedon the total amount of the refrigerator lubricating oil.

The base oil of the refrigerator lubricating oil preferably consistsonly of the polyoxyalkylene glycol compound represented by the generalformula (2).

The polyoxyalkylene glycol compound represented by the general formula(2) preferably has a kinetic viscosity at 40° C. of from 10 to 500mm²/s, and more preferably from 20 to 200 mm²/s.

The 100° C. kinetic viscosity thereof is preferably from 3 to 60 mm²/s,and more preferably from 5 to 30 mm²/s.

The viscosity index is preferably 100 or more, more preferably 150 ormore, and particularly preferably 180 or more, from the standpoint ofproviding good viscosity characteristics. The upper limit of theviscosity index is 300 since the effect of the viscosity characteristicsmay reach the peak.

The polyoxyalkylene glycol compound represented by the general formula(2) preferably has a hydroxyl value of 15 mgKOH/g or less. When thehydroxyl value is 15 mgKOH/g or less, the polyoxyalkylene glycolcompound represented by the general formula (2) may be appropriatelyprevented from being decomposed to provide good stability of therefrigerator lubricating oil. The hydroxyl value herein is measured bythe neutralization titration method according to JIS K0070.

<Phenothiazine Compound>

The refrigerator lubricating oil according to an embodiment of thepresent invention contains an additive in addition to the base oil. Inthe embodiment, a phenothiazine compound is contained in an amount of1.0% by mass or more based on the total amount of the refrigeratorlubricating oil. The upper limit of the amount thereof may be 10% bymass since the effect of increasing the autoignition point of therefrigerator lubricating oil may reach the peak. The amount of thephenothiazine compound blended is preferably 2% by mass or more and 7%by mass or less, more preferably 2% by mass or more and 5% by mass orless, and particularly preferably 3% by mass or more and 5% by mass orless, based on the total amount of the refrigerator lubricating oil,from the standpoint of the remarkable effect of increasing theautoignition point of the refrigerator lubricating oil.

The phenothiazine compound is preferably at least one selected frommethoxyphenothiazine, 2-(trifluoromethyl)phenothiazine,2-acetylphenothiazine, 1-azaphenothiazine, and a phenothiazine-styrenederivative, and among these, methoxyphenothiazine and aphenothiazine-styrene derivative are preferred, and methoxyphenothiazineis more preferred, from the standpoint of increasing the autoignitionpoint.

The autoignition point of the refrigerator lubricating oil is preferably370° C. or more, more preferably 380° C. or more, and particularlypreferably 390° C. or more, in terms of autoignition point measuredaccording to ASTM E659-78.

The increase of the autoignition point of the refrigerator lubricatingoil may also increase the autoignition point of the mixed compositionfor a refrigerator.

[Other Additives]

The refrigerator lubricating oil according to an embodiment of thepresent invention may be blended with, in addition to the base oil, atleast one additive selected from an extreme pressure agent, an oilyagent, an antioxidant, an acid scavenger, a defoaming agent, and thelike.

Examples of the extreme pressure agent include a phosphorus extremepressure agent, such as a phosphate ester, an acidic phosphate ester, aphosphite ester, an acidic phosphite ester, and amine salts thereof. Inthe phosphorus extreme pressure agent, tricresyl phosphate,trithiophenyl phosphate, tri(nonylphenyl) phosphite, dioleyl hydrogenphosphite, 2-ethylhexyldiphenyl phosphite, and the like are particularlypreferred from the standpoint of the extreme pressure property, thefrictional characteristics, and the like.

Examples of the extreme pressure agent also include a metal salt of acarboxylic acid. The metal salt of a carboxylic acid referred herein ispreferably a metal salt of a carboxylic acid having a number of carbonatoms of from 3 to 60, and further a fatty acid having a number ofcarbon atoms of from 3 to 30, and particularly from 12 to 30. Examplesthereof also include metal salts of a dimer acid and a trimer acid ofthe fatty acid, and a dicarboxylic acid having a number of carbon atomsof from 3 to 30. Among these, metal salts of a fatty acid having anumber of carbon atoms of from 12 to 30 and a dicarboxylic acid having anumber of carbon atoms of from 3 to 30 are particularly preferred. Themetal constituting the metal salt is preferably an alkali metal or analkaline earth metal, and particularly an alkali metal may be optimum.

Examples of the extreme pressure agent other than those described aboveinclude a sulfur extreme pressure agent, such as a sulfurized oil orfat, a sulfurized fatty acid, a sulfurized ester, a thiocarbamatecompound, a thioterpene compound, and a dialkyl thiodipropionatecompound.

The amount of the extreme pressure agent blended thereto is generallyfrom 0.001 to 5% by mass, and particularly from 0.005 to 3% by mass,based on the total amount of the refrigerator lubricating oil, from thestandpoint of the lubricating property and the stability.

The extreme pressure agent may be used solely or as a combination of twoor more kinds thereof.

Examples of the oily agent include an aliphatic saturated or unsaturatedmonocarboxylic acid, such as stearic acid and oleic acid, a polymerizedfatty acid, such as a dimer acid and a hydrogenated dimer acid, ahydroxyfatty acid, such as ricinoleic acid and 12-hydroxystearic acid,an aliphatic saturated or unsaturated monohydric alcohol, such as laurylalcohol and oleyl alcohol, an aliphatic saturated or unsaturatedmonoamine, such as stearylamine and oleylamine, and an aliphaticsaturated or unsaturated monocarboxylic acid amide, such as lauric acidamide and oleic acid amid.

These compounds may be used solely or as a combination of two or morekinds thereof. The amount thereof blended is generally selected from arange of from 0.01 to 10% by mass, and preferably from 0.1 to 5% bymass, based on the total amount of the refrigerator lubricating oil.

As the antioxidant, a phenol antioxidant, such as2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, and2,2′-methylenebis(4-methyl-6-tert-butylphenol), or an amine antioxidant,such as phenyl-α-naphthylamine and N,N′-diphenyl-p-phenylenediamine ispreferably blended. The amount of the antioxidant blended is generallyfrom 0.01 to 5% by mass, and preferably from 0.05 to 3% by mass, basedon the total amount of the refrigerator lubricating oil, from thestandpoint of the effect and the economic efficiency.

Examples of the acid scavenger include an epoxy compound, such as phenylglycidyl ether, an alkyl glycidyl ether, an alkylene glycol glycidylether, cyclohexene oxide, an α-olefin oxide and an epoxidized soybeanoil. Among these, phenyl glycidyl ether, an alkyl glycidyl ether, analkylene glycol glycidyl ether, cyclohexene oxide, and an α-olefin oxideare preferred from the standpoint of the compatibility.

The alkyl group of the alkyl glycidyl ether and the alkylene group ofthe alkylene glycol glycidyl ether each may have a branch, and eachgenerally has a number of carbon atoms of from 3 to 30, preferably from4 to 24, and particularly from 6 to 16. The α-olefin oxide usedgenerally has a total number of carbon atoms of from 4 to 50, preferablyfrom 4 to 24, and particularly from 6 to 16. In the present invention,the acid scavenger may be used solely or as a combination of two or morekinds thereof. The amount thereof blended is generally from 0.005 to 5%by mass, and particularly preferably from 0.05 to 3% by mass, based onthe total amount of the refrigerator lubricating oil, from thestandpoint of the effect and the prevention of sludge generated.

In the present invention, the use of the acid scavenger blended canenhance the stability of the refrigerator lubricating oil. Thecombination use thereof with the extreme pressure agent and theantioxidant can exhibit an effect of further enhancing the stability.

Examples of the defoaming agent include a silicone oil and a fluorinatedsilicone oil.

Other known additives may be blended to the refrigerator lubricating oilof the present invention in such a range that does not impair theobjects of the present invention.

The refrigerator lubricating oil may be mixed with a refrigerant to forma mixed composition for a refrigerator, which may be used in arefrigerator. In the mixed composition for a refrigerator, the massratio of the refrigerant with respect to the refrigerator lubricatingoil (refrigerator lubricating oil/refrigerant) is preferably in a rangeof from 90/10 to 1/99, more preferably from 70/30 to 5/95, and furtherpreferably from 60/40 to 5/95. The mass ratio within the range canprovide a good refrigeration capability and a lubricating performance ina well balanced manner.

[Lubricating Method and Refrigerator]

The lubricating method of the present invention is a lubricating methodcontaining using the aforementioned refrigerator lubricating oil in arefrigerator using the aforementioned refrigerant.

The refrigerator contains the refrigerant and the refrigeratorlubricating oil to be mixed with the refrigerant. The refrigerator has,for example, a compressor, a condenser, an expansion mechanism (such asan expansion valve), and an evaporator, or a compressor, a condenser, anexpansion mechanism, a dryer, and an evaporator, by which arefrigeration cycle is constituted. The refrigerant used by mixing withthe refrigerator lubricating oil is circulated in the refrigerationcycle, and repeatedly absorbs and releases heat. The refrigeratorlubricating oil lubricates the refrigerator, for example, a slidingportion and the like of the compressor.

The refrigerator of the present invention can be applied, for example,to a refrigeration system, a hot water supply system, or a heatingsystem, such as a car air-conditioner, a gas heat pump (GHP) system, anair conditioner, a refrigerating chamber, an automatic vending machine,a showcase, a hot water supplier, and a floor heating system, ispreferably used in a car air-conditioner, such as an electric carair-conditioner and an open type car air-conditioner, and isparticularly suitable for an open type car air-conditioner.

In the system, to which the refrigerator is applied, it is preferredthat the water content in the system is 300 ppm by mass or less, and theresidual air partial pressure therein of 10 kPa or less. The watercontent is more preferably 200 ppm by mass or less, and the residual airpartial pressure is more preferably 5 kPa or less.

EXAMPLES

The present invention will be described in more detail with reference toexamples and comparative examples below, but the present invention isnot limited to the examples.

[Evaluation Methods]

<Measurement Method of Autoignition point>

The measurement method of an autoignition point accorded to ASTME659-78.

The electric furnace and the temperature controller described in ASTME659, Standard Test Method for Autoignition Temperature Of LiquidChemicals, were used.

100 μL of a specimen of the refrigerator lubricating oil was collectedwith a syringe, and the presence of autoignition thereof was observedafter setting the flask to the assumed autoignition temperature. When noautoignition was observed at the setting temperature after the lapse of10 minutes, the observation was performed for 10 minutes after furtherincreasing the temperature. The operation was repeated by increasing thetemperature until autoignition was observed, and the temperature whereautoignition was observed was designated as the autoignition point.

An autoignition point of 370° C. or more was designated as passed.

Examples and Comparative Examples

Refrigerator lubricating oils containing a base oil and an additive wereprepared according to the formulations and the blending amounts shown inTables 1 to 5, and the autoignition points of the refrigeratorlubricating oils of Examples and Comparative Examples were measuredaccording to the aforementioned evaluation method. The results are shownin Tables 1 to 5.

Tables 1 to 5 are different in the kind of the phenothiazine compoundadded. The difference between Examples and Comparative Examples in eachof the tables is the difference in the blending amount of thephenothiazine compound added.

TABLE 1 Comparative Comparative Example 1 Example 2 Example 3 Example 4Example 5 Example 6 Example 1 Example 2 Refrigerator Base oil*¹ 99 98 9796 95 94 100 99.5 lubricating oil (% by mass) Phenothiazine 1 2 3 4 5 60 0.5 compound 1*² (% by mass) Result Autoignition 378 389 393 399 394394 367 368 point (° C.)

TABLE 2 Comparative Comparative Example 11 Example 12 Example 13 Example14 Example 15 Example 11 Example 12 Refrigerator Base oil*¹ 99 98 97 9695 100 99.5 lubricating oil (% by mass) Phenothiazine 1 2 3 4 5 0 0.5compound 2*³ (% by mass) Result Autoignition 371 375 379 385 388 367 368point (° C.)

TABLE 3 Comparative Comparative Example 21 Example 22 Example 23 Example24 Example 25 Example 21 Example 22 Refrigerator Base oil*¹ 99 98 97 9695 100 99.5 lubricating oil (% by mass) Phenothiazine 1 2 3 4 5 0 0.5compound 3*⁴ (% by mass) Result Autoignition 371 374 378 383 385 367 368point (° C.)

TABLE 4 Comparative Comparative Example 31 Example 32 Example 33 Example34 Example 35 Example 31 Example 32 Refrigerator Base oil*¹ 99 98 97 9695 100 99.5 lubricating oil (% by mass) Phenothiazine 1 2 3 4 5 0 0.5compound 4*⁵ (% by mass) Result Autoignition 370 372 377 380 382 367 368point (° C.)

TABLE 5 Comparative Comparative Example 41 Example 42 Example 43 Example44 Example 45 Example 41 Example 42 Refrigerator Base oil*¹ 99 98 97 9695 100 99.5 lubricating oil (% by mass) Phenothiazine 1 2 3 4 5 0 0.5compound 5*⁶ (% by mass) Result Autoignition 373 377 384 387 392 367 368point (° C.)

The notes in Tables 1 to 5 are as follows.

*1: polypropylene glycol dimethyl ether, 40° C. kinetic viscosity: 42.8mm²/s, 100° C. kinetic viscosity: 9.52 mm²/s, hydroxyl value: 0.9mgKOH/g

*2: methoxyphenothiazine

* 3: 2-(trifluoromethyl)phenothiazine

*4: 2-acetylphenothiazine

*5: 1-azaphenothiazine

*6: phenothiazine-styrene derivative (ST-FT)

[Evaluation Results]

As shown in Examples 1 to 6, 11 to 15, 21 to 25, 31 to 35, and 41 to 45,it was found that when the phenothiazine compound was contained in therefrigerator lubricating oil, the autoignition point was increased, ascompared to the one containing no phenothiazine compound and the onecontaining the phenothiazine compound in an amount less than 1.0% bymass. In particular, the better effect of increasing the autoignitionpoint was obtained when the blending amount of the phenothiazinecompound is 3.0% by mass or more and 5.0% by mass or less based on thetotal amount of the refrigerator lubricating oil.

1. A mixed composition for a refrigerator, the composition comprising: arefrigerant comprising at least one unsaturated fluorinated hydrocarboncompound represented by formula (1):C_(p)F_(r)H_(s)   (1), wherein p represents an integer of from 2 to 6; rrepresents an integer of from 1 to 11; and s represents an integer offrom 1 to 11, provided that the compound has one or more carbon-carbonunsaturated bond in a molecule; and a refrigerator lubricating oilcomprising, as a major component, a polyoxyalkylene glycol compoundrepresented by the following general formula (2), and comprising aphenothiazine compound in an amount of 1.0% by mass or more based on atotal amount of the refrigerator lubricating oil:R¹—[(OR²)_(m)—OR³]_(n)   (2), wherein: R¹ is a hydrogen atom, an alkylgroup having a number of carbon atoms of from 1 to 10, an acyl grouphaving a number of carbon atoms of from 2 to 10, an aliphatichydrocarbon group having a number of carbon atoms of from 1 to 10 andhaving from 2 to 6 bonding sites, or a substituent having a number ofcarbon atoms of from 3 to 15 and comprising a heterocyclic ring whichhas oxygen, sulfur, or both, as a heteroatom; R² independentlyrepresents an alkylene group having a number of carbon atoms of from 2to 4; R³ independently represents a hydrogen atom, an alkyl group havinga number of carbon atoms of from 1 to 10, or an acyl group having anumber of carbon atoms of from 2 to 10: n represents an integer of fromI to 6; and m represents a number such that an average value of m×n isfrom 6 to
 80. 2. The mixed composition for a refrigerator according toclaim 1, wherein the refrigerant consists of the unsaturated fluorinatedhydrocarbon compound.
 3. The mixed composition for a refrigeratoraccording to claim 1, wherein the unsaturated fluorinated hydrocarboncompound is a fluoride of propene.
 4. The mixed composition for arefrigerator according to claim 3, wherein the fluoride of propene is atleast one selected from the group consisting of isomers ofpentafluoropropene, 3,3,3-trifluoropropene, and1,3,3,3-tetrafluoropropene.
 5. The mixed composition for a refrigeratoraccording to claim 1, wherein the phenothiazine compound is at least oneselected from the group consisting of methoxyphenothiazine,2-(trifluoromethyl) phenothiazine, 2-acetylphenothiazine,1-azaphenothiazine, and a phenothiazine-styrene derivative.
 6. The mixedcomposition for a refrigerator according to claim 1, wherein therefrigerant comprises at least one saturated fluorinated hydrocarboncompound selected from the group consisting of 1,1-difluoroethane,trifluoroethane, tetrafluoroethane, and pentafluoroethane.
 7. The mixedcomposition for a refrigerator according to claim 1, wherein the mixedcomposition is adapted to function as a mixed composition for a hotwater supply system or a refrigerating and heating system of a carair-conditioner, an electric car air-conditioner, a gas heat pumpsystem, an air conditioner, a refrigerating chamber, an automaticvending machine, or a showcase.
 8. The mixed composition for arefrigerator according to claim 1, wherein the mixed composition isadapted to function as a mixed composition for a car air-conditioner oran electric car air-conditioner.
 9. The mixed composition for arefrigerator according to claim 1, wherein the mixed composition isadapted to function as a mixed composition for a hot water supply systemor a refrigerating and heating system, and the system has a watercontent therein of 300 ppm by mass or less and a residual air partialpressure therein of 10 kPa or less.
 10. A refrigerator lubricating oilthat is suitable for a refrigerant comprising at least one unsaturatedfluorinated hydrocarbon compound represented by formula (1):C_(p)F_(r)H_(s)   (1), wherein p represents an integer of from 2 to 6; rrepresents an integer of from 1 to 11; and s represents an integer offrom 1 to 11, provided that the compound has one or more carbon-carbonunsaturated bond in a molecule, the refrigerator lubricating oilcomprising, as a major component, a polyoxyalkylene glycol compoundrepresented by formula (2), and comprising a phenothiazine compound inan amount of 1.0% by mass or more based on a total amount of therefrigerator lubricating oil:R¹—[(OR²)_(m)—OR³]_(n)   (2), wherein: R¹ is a hydrogen atom, an alkylgroup having a number of carbon atoms of from 1 to 10, an acyl grouphaving a number of carbon atoms of from 2 to 10, an aliphatichydrocarbon group having a number of carbon atoms of from 1 to 10 andhaving from 2 to 6 bonding sites, or a substituent having a number ofcarbon atoms of from 3 to 15 and comprising a heterocyclic ring whichhas oxygen, sulfur, or both, as a heteroatom; R² independentlyrepresents an alkylene group having a number of carbon atoms of from 2to 4; R³ independently represents a hydrogen atom, an alkyl group havinga number of arbon atoms of from 1 to 10, or an acyl group having anumber of carbon atoms of from 2 to 10; n represents an integer of from1 to 6; and m represents a number such that an average value of m×n isfrom 6 to
 80. 11. A method, comprising lubricating a refrigerator with arefrigerator lubricating oil, wherein: the refrigerator comprises arefrigerant comprising at least one unsaturated fluorinated hydrocarboncompound represented by formula (1):C_(p)F_(r)H_(s)   (1), wherein p represents an integer of from 2 to 6; rrepresents an integer of from 1 to 11; and s represents an integer offrom 1 to 11, provided that the compound has one or more carbon-carbonunsaturated bond in a molecule; and the refrigerator lubricating oilcomprises as a major component, a polyoxyalkylene glycol compoundrepresented by formula (2), and comprising a phenothiazine compound inan amount of 1.0% by mass or more based on a total amount of therefrigerator lubricating oil:R¹—[(OR²)_(m)—OR³]_(n)   (2), wherein: R¹ is a hydrogen atom, an alkylgroup having a number of carbon atoms of from 1 to 10, an acyl grouphaving a number of carbon atoms of from 2 to 10, an aliphatichydrocarbon group having a number of carbon atoms of from 1 to 10 andhaving from 2 to 6 bonding sites, or a substituent having a number ofcarbon atoms of from 3 to 15 and comprising a heterocyclic ring whichhas oxygen, sulfur, or both, as a heteroatom: R² independentlyrepresents an alkylene group having a number of carbon atoms of from 2to 4; R³ independently represents a hydrogen atom, an alkyl group havinga number of carbon atoms of from 1 to 10, or an acyl group having anumber of carbon atoms of from 2 to 10; n represents an integer of from1 to 6; and m represents a number such that an average value of m×n isfrom 6 to
 80. 12. A refrigerator, comprising: a refrigerant comprisingat least one unsaturated fluorinated hydrocarbon compound represented byformula (1):C_(p)F_(r)H_(s)   (1), wherein p represents an integer of from 2 to 6; rrepresents an integer of from 1 to 11; and s represents an integer offrom 1 to 11, provided that the compound has one or more carbon-carbonunsaturated bond in a molecule; and a refrigerator lubricating oilcomprising, as a major component, a polyoxyalkylene glycol compoundrepresented by formula (2), and comprising a phenothiazine compound inan amount of 1.0% by mass or more based on a total amount of therefrigerator lubricating oil:R¹—[(OR²)_(m)—OR³]_(n)   (2), wherein R¹ is a hydrogen atom, an alkylgroup having a number of carbon atoms of from 1 to 10, an acyl grouphaving a number of carbon atoms of from 2 to 10, an aliphatichydrocarbon group having a number of carbon atoms of from 1 to 10 andhaving from 2 to 6 bonding sites, or a substituent having a number ofcarbon atoms of from 3 to 15 and comprisin a heterocyclic ring which hasoxygen, sulfur, or both, as a heteroatom; R² independently represents analkylene group having a number of carbon atoms of from 2 to 4; R³independently represents a hydrogen atom, an alkyl group having a numberof carbon atoms of from I to 10, or an acyl group having a number ofcarbon atoms of from 2 to 10; n represents an integer of from 1 to 6;and m represents a number such that an average value of m×n is from 6 to80.